adv7188 Analog Devices, Inc., adv7188 Datasheet - Page 77

• Manufacturer Part Number: adv7188
• Description: Multiformat Sdtv Video Decoder With Fast Switch Overlay Support
• Manufacturer: Analog Devices, Inc.

LB_TH [4:0], Letterbox Threshold Control,
Address 0xDC [4:0]
Table 97. LB_TH [4:0] Function
LB_TH [4:0]
01100
01101 to
00000 to
LB_SL [3:0], Letterbox Start Line, Address 0xDD [7:4]
The LB_SL [3:0] bits are set at 0100 by default. For an NTSC
signal, the letterbox detection is from Line 23 to Line 286.
By changing the bits to 0101, the detection starts on Line 24 and
ends on Line 287.
LB_EL [3:0], Letterbox End Line, Address 0xDD [3:0]
The LB_EL [3:0] bits are set at 1101 by default. This means that
letterbox detection ends with the last active video line. For an
NTSC signal, the detection is from Line 262 to Line 525.
By changing the settings of the bits to 1100, the detection starts
on Line 261 and ends on Line 254.
IF Compensation Filter
IFFILTSEL [2:0], IF Filter Select, Address 0xF8 [2:0]
The IFFILTSEL [2:0] register allows the user to compensate for
SAW filter characteristics on a composite input, such as those
associated with tuner outputs. Figure 44 and Figure 45 show IF
filter compensation for NTSC and PAL.
The options for this feature are as follows:
•
•
•
See Table 105 for programming details.
(default)
10000
01011
Bypass mode (default)
NTSC—consists of three filter characteristics
PAL—consists of three filter characteristics
Description
Default threshold for detection of black lines.
Increase threshold (need larger active video
content before identifying nonblack lines).
Decrease threshold (even small noise levels can
cause the detection of nonblack lines).
Rev. A | Page 77 of 112
I
The ADV7188 has a comprehensive interrupt register set. This
map is located in the user sub map. See Table 107 for details of
the interrupt register map. Figure 48 describes how to access
this map.
2
C Interrupt System
–10
–12
–2
–4
–6
–8
–2
–4
–6
–8
6
4
2
0
6
4
2
0
2.0
3.0
Figure 44. NTSC IF Compensation Filter Responses
Figure 45. PAL IF Compensation Filter Responses
2.5
3.5
3.0
4.0
FREQUENCY (MHz)
FREQUENCY (MHz)
3.5
4.5
4.0
5.0
4.5
5.5
ADV7188
5.0
6.0